The purpose of this project is to compare the hormonal control of oviduct contraction in two oviparous lizards, Hemidactylus frenatus and Anolis carolinensis. The former species exhibits simultaneous oviposition, whereas the latter alternates oviposition from side to side. Thus, the endocrine control of oviposition may differ in the two species. The effects of arginine vasotocin on oviductal contraction will be examined in vivo and in vitro. Also, the role of corpora lutea in influencing oviductal contractions will be determined by deluteinization, morphological analyses of corpus luteum activity, radioimmunoassay of steroid hormone levels in the blood, and study of oviductal-ovarian vascular connections.